mm/memory.c:zap_pte_range() print bad swap entry

We have a report of this WARN() triggering.  Let's print the offending
swp_entry_t to help diagnosis.

Link: https://lkml.kernel.org/r/[email protected]
Cc: Muhammad Usama Anjum <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/memory.c

@@ -1517,6 +1517,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
  continue;
  } else {
  /* We should have covered all the swap entry types */
+ pr_alert("unrecognized swap entry 0x%lx\n", entry.val);
  WARN_ON_ONCE(1);
  }
  pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);